The click sound playback is a technology of, when a user operated onto a GUI that is displayed while a motion picture is played back, mixing a click sound with a playback sound/voice of the motion picture and outputting the mixed sound/voice.
For example, when the GUI, displayed while a motion picture is played back, can receive an instruction to perform a function like “game start” from the user, an audio announce “Let's play the game!!” may be mixed, as the click sound, with the playback sound/voice of the motion picture, and the mixed sound/voice may be output. In such a case, if the audio announce is a voice of a character appearing in the motion picture, the user, especially when he/she is a child, will have an impression that he/she is talked to by the character appearing in the motion picture. With the introduction of such a click sound, it is possible to provide the motion picture with a GUI that make children fun.
The following Document 1 discloses a technology for mixing an audio output with another audio output and outputting a mixed sound/voice.    Document 1: Japanese Patent Application Publication No. 7-320411